Moving beyond the (US) Federal law and regulations, there are many other sources of guidance for the ethical and humane use of animals in laboratory research. One of these which gradually gained a status that is now similar to official law is the Guide for the Care and Use of Laboratory Animals.

The Guide, often called "The NIH Guide", is published by the National Academy Press as a work credited to committees of the Institute for Laboratory Animal Resources, the Commission on Life Sciences and the National Research Council. As the ILAR site informs us:

The Guide's recommendations carry the force of law based on the Health Research Extension Act passed by Congress in 1985.

The Guide is available here, where it can be navigated page by page if you are patient, or purchased. One free copy may be requested from the Office of Laboratory Animal Welfare of the NIH. This ILAR page also indicates that the Guide is available in several language translations as it has come to be used worldwide. If you read journal articles which include animal research it is very likely that you are used to seeing a statement similar to this in the Subjects section of the Materials and Method: "These studies followed the guidelines of the NIH Guide and were conducted under a protocol approved by the IACUC of the University of Whatsit." Indeed, many journals require that an explicit statement of concordance with the Guide be made prior to accepting a manuscript submission for review.
The current version of the Guide, issued in 1996, is getting a bit long in the tooth and there is a a two year effort under way to create the next revision. According to the Preface of the 1996 version, the Guide was published in 1963 as Guide for Laboratory Animal Facilities and Care and was revised in 1965, 1968, 1972 and 1985. Prior versions were apparently funded exclusively by the NIH, hence the shorthand reference to "the NIH Guide".
The Guide has major chapters on Institutional Policies and Responsibilities, Animal Environment, Housing and Management, Veterinary Medical Care and Physical Plant.
One of the most important concepts for those new to animal research to appreciate is laid out on page 3 in the introductory remarks.

The Guide charges users of research animals with the responsibility of achieving specified outcomes but leaves it up to them how to accomplish these goals. This ''performance" approach is desirable because many variables (such as the species and previous history of the animals, facilities, expertise of the people, and research goals) often make prescriptive ("engineering") approaches impractical and unwarranted.
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The Guide is deliberately written in general terms so that its recommendations can be applied in the diverse institutions and settings that produce or use animals for research, teaching, and testing; generalizations and broad recommendations are imperative in such a document. This approach requires that users, IACUCs, veterinarians, and producers use professional judgment in making specific decisions regarding animal care and use. Because this Guide is written in general terms, IACUCs have a key role in interpretation, oversight, and evaluation of institutional animal care and use programs.

Results rather than rules, so to speak. Performance versus engineering standard is a fairly frequent topic of discussion when it comes to animal use in research, IME. You can imagine that this is a point of contention from all sides with respect to this local-control approach. Critics argue that differences in practices from site A to site B show there is a problem. On the other hand, scientists who are in a more-restrictive environment argue that less-restrictive practices their colleague works under halfway across the country should apply to them too (sometimes). People argue for greater specificity of standards when if follows their interest, but not when it does not. (If you lack imagination as to why a animal care advocate wouldn't want greater specificity of standards, think about a situation where all the prescriptive rules were followed but for whatever reasons a rare animal was in obvious distress- rule following would be no excuse.)
To give you a slight flavor of how the Guide offers a refinement of the USDA/APHIS regulations, I'll contrast Title 9 -- Animals and Animal Products; Chapter 1 -- Animal and Plant Health Inspection Service, Department of Agriculture; PART 3 -- STANDARDS; Subpart F- Specifications for the Humane Handling, Care, Treatment, and Transportation of Warmblooded Animals Other Than Dogs, Cats, Rabbits, Hamsters, Guinea Pigs, Nonhman Primates, and Marine Mammals (read, those excepted by the Helms amendment); 3.128 Space requirements:

Enclosures shall be constructed and maintained so as to provide sufficient space to allow each animal to make normal postural and social adjustments with adequate freedom of movement. Inadequate space may be indicated by evidence of malnutrition, poor condition, debility, stress, or abnormal behavior patterns.

with Table 2.1 from the Guide:
There are additional specifications of space requirements for other species, ambient temperature ranges and humidity and a discussion of ventilation. Food, bedding, water, social environment, all husbandry parameters receive attention in the Guide. Since this is freely available, I'm not going to belabor the point. Except to note that this is the sort of information the researcher needs to know quite well. What size caging do you require for your species, does this change with age/size? What control over ambient temperature and humidity do you need, at what deviation should the building HAVAC alarms go off? What social or other enrichment do you need to provide? What size rooms? How do the floors and walls need to be painted/sealed? Etc.
Not all of this is in your power to change as an individual investigator, of course. But for new PIs, when they show you your new space at your new University, you should have a clue because they may not. Especially if the hiring department isn't really an animal-research department. Or if they haven't dealt with your species before and, for example, don't realize that your hopping Bunnies are governed as a USDA species, not a Helms Amendment species.
You will note that there are a few more interesting bit in the Guide including discussion of analgesia, anesthesia, experimental surgeries and euthanasia. I'm holding off on those for the discussion of the animal protocol, which we're approaching quickly.

For the UC system, anyone who has any sort of contact with animals (in or out of the lab) during research has to get qualified. The NIH guide (and a little test to verify you have at least skimmed it) are part of that.
I actually really approve of the generality of it. Specific info and guidelines are useful, but 'best practices' can quickly outpace the guidelines. And it is simply impossible to cover every species and/or situation. The researchers are generally smart people after all, and one requirement (IIRC) is having a competent vet around/on call to help with the specifics.

Oh, are there eithics in legalized animal cruelty? Don't think so. Anyone who purposely inflicts pain, terror and suffering upon helpless animals then coldly watches the results of their torture has no ethics, morals - needless to say compassion. Disgusting animal torturers, supported and funded by our tax dollars and condoned by a consumer crazed society. NIH and their "Cruel kindness" ...What a joke!

oh dear, another balanced comment from a neutral observer. I hope you are in good health Jen- because avoiding treatments that have been tested on animals will be difficult- perhaps you should try homeopathy, or would you prefer hypocrisy like many others.
DrugMonkey- try working in britain where this is all enshrined in law- if you don't comply you don't work full stop.